Antoni Leja's "storm in a test tube"
A reaction of potassium permanganate, sulfuric acid, and ethanol creates a violent and colorful chemical "storm" complete with bursts of "lightning" and "microthunder."
Ingredients: potassium permanganate crystals, concentrated (98%) sulfuric acid, pure ethanol, test tube, glass stirring rod
Procedure: A minimal recipe follows.
1. Carefully pour concentrated sulfuric acid into a test tube, using a glass stirring rode to guide the acid to the bottom. It is essential that the acid does not touch the sides of the test tube.
2. Gently pour ethanol atop the sulfuric acid.
3. Add crystals of potassium permanganate.
Understanding: The sulfuric acid acts to reduce the manganese(VII), in the potassium permanganate, to manganese(IV). The first reaction involves the transformation of the permanganate ion to manganese(VII)oxide
KMnO4(s) + H2SO4(aq) → K2SO4(aq) + Mn2O7(s) + H2O(l)
followed by the reduction of the manganese(VII)oxide to manganese(IV)oxideMn2O7(s) → MnO2(s) + O2(g)
This reaction is exothermic and the use of a heat bath (the surrounding bowl of water) is absolutely essential to maintain the stability of the chemical system.
A product of this reaction is dioxygen. The bubbles of dioxygen gas rise from the reaction interface into the neat ethanol. The combination of volatile alcohol, molecular oxygen, and heat results in storm of random and intense bursts of light.
Using a sufficient quantity of potassium permanganate, the reaction can be maintained for some time. Before the reaction mixture is disposed of, the reaction must be allowed to run to completion. Allow the reaction mixture to sit overnight. The next day, gently stir the solution, carefully checking the temperature of the solution. If a great deal of heat is evolved, stop stirring! Let the mixture react further. Repeat your careful stirring, again monitoring the temperature. Once the mixture can be vigorously stirred without evolving a substantial quantity of heat, the solution is ready for proper disposal.